The 2012 Mac Pro has a built-in optical drive, so once I had the CD available, I popped it in and rebooted the Mac Pro. When rebooting, I held down the Option key to allow the various boot drive options to appear, then selected the CD. The CD showed up with EFI Boot and Windows partitions, so I selected EFI Boot.

NOTE: All screenshots of this process are from ESXi running inside of VMWare Fusion, but the upgrade process on my Mac Pro was identical.

Once booted from the CD, I was asked to select the ESXi 6.x installer. Once selected, the ESXi installer boot process began.

1. When asked to begin the installation process, I hit the Enter key on my keyboard.

2. I hit the F11 key on my keyboard to accept the license agreement.

At this point, the installer took a few minutes to scan the machine.

3. Once scanning completed, I was asked to select the drive I wanted to install on. I selected the drive I wanted and hit the Enter key.

4. A VMFS partition was detected, so the installer did additional scanning of that partition.

5. I was notified that an existing ESXi installation and datastore was detected and I was given several options. I chose to upgrade ESXi and preserve the existing datastore, then hit the Enter key on my keyboard.

At this point, the installer took a few minutes to scan the machine again.

6. The installer then confirms that I wanted to to upgrade ESXi using the options I had selected. I hit the F11 key on my keyboard to confirm.

7. The installer then upgraded the existing ESXi installation to ESXi 6.x.

8. When the upgrade has completed, the installer requested that the installation disc be removed before rebooting. I removed it, then hit the Enter key on my keyboard to reboot.

NOTE: As you’re upgrading from an earlier version of ESXi, your current ESXi license will need to be updated to one for ESXi 6.x. The ESXi upgrade process will automatically install a a 60 day evaluation license.

8. After the reboot, my ESXi server was now running ESXi 6.0

As mentioned previously, an upgraded ESXi server will initially be using a a 60 day evaluation license. If you’re using VMware’s free license for ESXi, you can log in to the VMWare website and download a free ESXi 6.x license to use with your ESXi server.